The present invention relates to the microscope art and, more particularly, to an improved low-profile cutter assembly for use on a microscope.
When viewing a specimen on the stage of a microscope, isolating a single cell or cutting a spore is sometimes necessary. However, as should be recognized, using a conventional knife or scalpel to make the delicate, precise cut required is difficult. This is especially true when very small or even microscopic specimens are presented, which are susceptible to loss or destruction if the cutting operation is improperly performed.
To solve this problem, others in the past have proposed remotely actuated cutter devices for mounting directly to the microscope. One popular form of such a device was developed by Dr. J. R. Raper of Harvard University in the early 1960""s. Dr. Raper""s cutter device includes a mounting ring for attachment to the objective of the microscope and a downwardly depending fixed-height arm having a yoke for receiving and supporting a pivotally mounted cutter blade. A cable actuator extends through a passage in the mounting ring and attaches to the pivoting blade. Upon actuating the cable, the blade pivots toward the slide, plate, or other specimen present on the microscope stage. Thus, using this cutter device, a cell or spore in the specimen can be easily isolated with a minimum amount of effort.
Although Dr. Raper""s cutter device is a great improvement over the manual use of scalpels, knives or the like, some limitations have been observed, especially with the advent of modern, more compact microscopes. More specifically, modern microscopes typically have a much shorter working distance between the objective and the stage than their older counterparts (about 10 millimeters as opposed to 30 millimeters). Thus, Dr. Raper""s proposed device, which includes a depending arm having a fixed height of around 30 millimeters, cannot be used in such an arrangement. Absent a complete redesign, this leaves two options: (1) produce a series of specialized cutter devices having different dimensions, each for use on a particular type of microscope; or (2) purchase a special objective of a type known in the art that provides a minimum working distance of about 25 millimeters. Of course, the former option is expensive, as a variety of cutter devices must be kept on hand for use with different types of microscopes. The latter alternative is also expensive and would still be inadequate to accommodate the 30 millimeter depending arm of Dr. Raper""s cutter device.
Accordingly, a need is identified for an improved cutter device for use on a microscope that overcomes the above-described limitations. Specifically, the device would be ready for use on many modern microscopes, including those having shorter working distances between the objective and the stage.
In accordance with the purposes and objectives of this invention, a cutter assembly for use on a microscope is provided. The cutter assembly has a very low profile, but can still supply the cutting force necessary to complete the desired operation smoothly and with a minimum amount of effort. This low profile advantageously permits use of the cutter assembly on a wider variety of modern microscopes than possible with prior art cutter devices, such as the one proposed by Dr. Raper, without the need for extensive retrofitting, adjustment or expense. However, the overall reliability and operational characteristics, including the amount of cutting force supplied, remain uncompromised.
In the preferred embodiment, the cutter assembly includes a support subassembly and a cutter subassembly. The support subassembly includes a forward annular mounting ring having attachment means for securing it to the periphery of the objective. Parallel side wings depend from the support subassembly and include corresponding opposed lateral slots for receiving lugs projecting from both sides of a first member, or cutter body, forming a part of the cutter subassembly. These lugs slide along the slots and allow the cutter subassembly to move between a home and forward position relative to the support subassembly. The forward portion of the cutter body carries a cutter, preferably in the form of a blade or other cutting implement. A separate second member, or connector body, also forms a part of the cutter subassembly. The cutter body pivots relative to the connector body when the cutter subassembly reaches the forward position. As a result of this pivoting, the cutter body moves towards the stage such that the cutter is adjacent to or in contact with the specimen. In the preferred embodiment, this pivoting motion is the result of engagement between corresponding camming surfaces provided on the connector body and the cutter body.
To move the cutter subassembly to and fro between the home position and the forward position, as well as to cause the cutter to pivot toward the stage, an actuator is provided. Preferably, this actuator is in the form of a cable extending through a guide carried by the support subassembly. One end of the cable is attached to the rear end of the connector body. The opposite end preferably includes an enlarged head to facilitate manual or tactile engagement by the microscope user.
To assist the cutter body in pivoting in a controlled fashion relative to the connector body and performing the desired cutting operation upon reaching the forward position, one or more biasing means is provided. More specifically, and in accordance with one preferred embodiment of the present invention, a first biasing means, such as a helical compression spring, connects the cutter body to the connector body. A second biasing means, such as a partially curved plate spring, is positioned between the cutter body and the support subassembly. As will be understood upon reviewing the description that follows, the first and second biasing means together assist in guiding the cutter body as the cutter subassembly is moved to the forward position by the actuator cable and ensure that the desired cutting function is smoothly and reliably provided.
In operation and in accordance with the related cutting method, the actuator cable is pushed through the guide to move the cutter subassembly forward such that the lugs slide forward in the corresponding slots in the support subassembly in a first plane. Upon reaching the terminal ends of these slots, additional pushing on the cable compresses the first biasing means, or helical compression spring, connecting the cutter body and the connector body. The resulting force biases the cutter body toward the home position, which causes the corresponding camming surfaces on the cutter body and connector body to engage each other. As a result of this camming action, the front end of the cutter body pivots toward the stage in a second plane, which places the blade or other cutter adjacent to or in actual contact with the specimen. At the same time, and also as a result of the camming action provided, the rear end of the cutter body pivots upwardly relative to the connector body. The rear end of the cutter body then engages the second biasing means, or plate spring, which in the preferred embodiment is attached to the support subassembly. The biasing force advantageously assists in controlling the pivoting motion of the opposite end of the cutter body toward the stage.
As should now be fully appreciated, one of the significant advantages afforded by the present invention is that the low profile cutter assembly may be used or a modern compound microscope having a shorter working distance between the objective and the stage. Not only does this provide the desired usage that is missing from known prior art cutter devices, but it also avoids the need for special objectives or other expensive and time consuming retrofitting procedures. Despite this low profile design, the cutter assembly can still produce the cutting force necessary to cut a spore or isolate a specimen in an efficient and effective manner.